Simulation of moisture distribution pattern in surface drip Irrigation system using dimension analysis

Simulation of moisture distribution pattern in the root zone and accurate determination for design can be considered as one of the criteria for improving yield productivity and utilization management in surface irrigation systems. In this study, experiments were carried out in a transparent plexy-glass physical model (0.5×1.22× 3 m) on three different soil textures (fine, heavy and medium). The emitter outflows were considered as 2.4, 4 and 6 l/hr with irrigation duration of 6 hrs. Then, using the p theorem of Buckingham and Dimension Analysis (DA), equations were developed to estimate the pattern of moisture distribution (horizontal and vertical) in three soil textures in subsurface drip irrigation. These equations were as function of initial moisture, radial distance of points, applied water volume, hydraulic conductivity and emitter outflows. Comparison between simulated and observed values showed that these equations are capable in predicting the pattern of moisture distribution in different directions. The average of Root Mean Square Error (RMSE) values in clay soil and for emitter outflows 2.4, 4 and 6 l/hr were 0.039, 0.08 and 0.036, respectively. These values for loamy soil were 0.15, 0.044 and 0.091, respectively; while for sandy soil were 0.018, 0.019 and 0.02, respectively. Using these equations in designing surface drip irrigation systems, the moisture distribution could be simply simulated and optimum management can be accordingly applied.